ClipboardHelper.h

// sktoolslib - common files for SK tools

// Copyright (C) 2012, 2020 - Stefan Kueng

// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software Foundation,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//

#pragma once

class CClipboardHelper
{
public:
    CClipboardHelper()
        : bClipBoardOpen(false)
    {
    }
    ~CClipboardHelper();
    bool           Open(HWND hOwningWnd, bool retry = true);
    static HGLOBAL GlobalAlloc(SIZE_T dwBytes);

private:
    bool bClipBoardOpen;
};

inline CClipboardHelper::~CClipboardHelper()
{
    if (bClipBoardOpen)
        CloseClipboard();
}

inline bool CClipboardHelper::Open(HWND hOwningWnd, bool retry)
{
    // OpenClipboard may fail if another application has opened the clipboard.
    // Try up to 8 times, with an initial delay of 1 ms and an exponential back off
    // for a maximum total delay of 127 ms (1+2+4+8+16+32+64).
    const int tries = retry ? 8 : 1;
    for (int attempt = 0; attempt < tries; ++attempt)
    {
        if (attempt > 0)
        {
            ::Sleep(1 << (attempt - 1));
        }
        bClipBoardOpen = (OpenClipboard(hOwningWnd) != 0);

        if (bClipBoardOpen)
        {
            return true;
        }
    }
    return false;
}

inline HGLOBAL CClipboardHelper::GlobalAlloc(SIZE_T dwBytes)
{
    return ::GlobalAlloc(GMEM_MOVEABLE, dwBytes);
}